Welcome, but sorry you have need to be here. And congratulations on the new baby! I know postpartum just adds a whole other layer of complicated on top of everything else. While I agree on not making hasty decisions, I think you know your judgment about his alcoholism is sound. Definitely don't act on anything immediately, but maybe consult an attorney (most first appointments are free) to find out what your rights are as his wife. You don't have to do anything with the information, but at least you'll have it.
My best tip would be to set up your support system. You've already gotten a start on that by posting here. My other tip is to cut yourself some slack. Even the smartest of us have ended up in unhealthy relationships. Addicts and abusers are masters at their game. We may have gotten swindled into it, but that doesn't mean we're stuck. Practice self care; focus your energy on taking care of yourself and that sweet baby of yours. It sounds like you're on the right track. You may slip and backslide a bit, and that's ok. Allow yourself to make mistakes, but be sure to learn from them. You have my support, as well as that of so many wonderful people here at SR.
I wish I could bottle That New Baby Smell. Nothing in the world like it.